In threshing operations carried out in combine harvesters, harvest residues are produced, normally consisting of chaff and straw from such crops as wheat, barley, oats and rye but also originating from different kinds of oil-producing plants and maize, sunflower and so on having comparatively large and stiff plant parts. For the sake of simplicity and clarity, the terms chaff and straw will, however, be used throughout.
Modern combine harvesters are becoming increasingly larger with increasingly wider cutting tables that are in themselves substantially wider than the combine itself. During the threshing operation considerable amounts of smoke and dust are generated around the combine, which is a serious problem as regards the combine drive motor and above all considering the substantial fire hazard involved. In order to minimise this hazard it important that the largest possible amounts of the harvest residues consisting of straw and chaff are spread as far as possible laterally and rearwards of the combine.
The chaff discharger connected to the combine sieving unit on the whole has the same width as the combine itself and conventionally it is designed to spread, following the threshing operation, the chaff laterally and rearwards across an area that essentially corresponds to the width of the cutting table. A straw chopper, usually a rotary cutter, which is connected to a straw shaker or threshing cylinder incorporated in the combine and which is located downstream of said drum, likewise has a width approximately equalling that of the combine itself, and conventionally it is designed to chop up the straw into smaller pieces after the threshing operation, and to spread the chopped straw across an area behind the combine that essentially equals the chaff spreading width. Following the spreading of the chaff and the chopped straw as indicated above, the chaff and the straw are as a rule ploughed down together into the ground.
If for various reasons it is not desired to chop the straw in the straw chopper but instead to deposit it in windrows on the ground behind the combine to be later collected, and preferably baled, for use for example as fodder, bedding material and the like, this could be effected with the aid of for example a deflector plate. In this case the deflector plate may be pivotal between a first position, wherein it closes an inlet to the straw-cutter housing to shunt the straw chopper and allow the unchopped straw to be windrowed, and a second position, wherein it exposes the inlet to allow chopping of the straw in the straw chopper and spreading of the chopped straw.
From SE-C2-512 815 is previously known a combine harvester of the type described above in general terms, the straw chopper of which is positioned downstream not only of the straw shaker unit or the threshing cylinder but also of the chaff discharger. In this case the deflector plate is disposed between the chaff spreader and the straw chopper and it is movable between the above two positions for windrowing and for chopping of the straw. Irrespective of the deflector plate position, the chaff discharge opening formed in the fan housing of the chaff discharger is arranged, by rotation of the fan housing, to be set in a first position, wherein the chaff is sspread across the ground, and a second position, wherein the chaff is mixed in with the unchopped straw.
When the chaff is to be mixed with the straw that is intended for windrowing, this operation is carried out with the deflector plate assuming its first position and the chaff discharge opening its second position, whereas on the other hand, when the chaff is to be mixed with the straw to be choppe, i.e. upstream of the straw chopper, this operation is carried out with the deflector plate and the chaff discharge opening assuming their respective second positions. To allow admixture of chaff into the straw in the latter situation, the deflector plate is formed with a chaff through-passage that may be opened and closed. The through-passage is open, when the deflector plate assumes its second position for chopping the straw, and is closed, when it assumes its first position for windrowing of the straw.
In some types of combine harvesters, various circumstances, such as lack of space or different structural or functional/technical solutions, make it very difficult or even impossible to so locate the chaff discharger that without problems the chaff may be mixed with or blown into the straw, to be chopped in the straw chopper, upstream of the latter.
Furthermore, in some cases, particularly when large volumes of chaff (and husks) are to be handled, it may be difficult satisfactorily and without unnecessary waste to blow the chaff through the open through-passage in the deflector plate to the straw chopper.
In addition, because the chaff is mixed into the straw to be chopped upstream of the straw chopper it may in some cases happen, for example when the volumes of straw and chaff are large or when the moisture contents of that material are high, that the straw chopper becomes overloaded or clogged. In turn, this may lead to impaired spreading of the chopped straw jointly with the at least partly chopped chaff and, if the worst comes to the worst, even to breakdown.
SE-A1-000382-2 disclosed a combine harvester, wherein a spreader formed with spreader wings for spreading the chopped straw across the ground is connected to the outlet of the straw chopper. In order to solve the problem outlined above, the chaff discharge opening in the fan housing of the chaff discharger is then arranged to be directed towards a first position, wherein the chaff may be blown into the spreader to be spread by the latter, and a second position for spreading the chaff laterally upstream of the spreader. Normally, setting the chaff discharge opening such that it is directed to either the first or the second position is effected by rotation of the fan housing, but alternatively it could be effected by forming the chaff discharger with a first outlet in the first position and a second outlet in the second position, both outlets-being openable and closable as desired for example with the aid of e.g. shutters or dampers.
Irrespective of the design of the combine harvester as discussed above or also corresponding combine types, setting or directing the chaff discharge opening between the first and second positions, respectively, by means of rotation of the chaff discharger fan housing require that the fan housing be controlled. If the housing is controlled manually, then the operator needs to leave the driver's cabin each time the fan housing is to be rotated, and walk to the chaff discharger at the rear end of the combine harvester and to return the cabin to continue the threshing operation. On the other hand, when the control is effected by electrical or hydraulic means or in some other way by means of controls installed in the driver's cabin, the operator need not leave the driver's cabin but on the other hand, rather expensive and complex installation of the controls in the cabin is required as also mounting of the drive means in the form of motors, valves and so on on the chaff discharger in order to rotate the associated fan housing, as well as operational lines/hoses/tubes extending between the driver's cabin and the chaff discharger.